samedi 17 octobre 2015

Image above: Scientists produced new global maps of Jupiter using the Wide Field Camera 3 on NASA's Hubble Space Telescope. One color map is shown here, projected onto a globe and as a flat image. Image credits: NASA/ESA/GSFC/UCBerkeley/JPL-Caltech/STScI.

New maps of Jupiter, produced using images from NASA's Hubble Space Telescope, provide a detailed window on the giant planet's dynamic features. The views come as the agency prepares for its Juno mission to arrive at Jupiter in a little less than a year.

The maps are the first in a planned series of yearly portraits of the solar system's four giant, outer planets, and are intended help scientists monitor how these worlds change over time.

Jupiter in 4k Ultra HD

The Jupiter maps are of particular interest to scientists working on Juno, which will arrive at Jupiter on July 4, 2016. "We've been coordinating with professional and amateur astronomers for several years now to collect observations that will help us plan Juno's activities once we arrive at Jupiter. The new Hubble maps are an extraordinarily valuable part of that effort," said Glenn Orton, a co-author on the paper from NASA's Jet Propulsion Laboratory in Pasadena, California.

Already, the Jupiter images have revealed a rare wave just north of the planet's equator and a unique filamentary feature in the core of the Great Red Spot not seen previously. They also reveal that the red spot continues its shrinking trend of recent years, becoming more circular and changing from red to a paler orange.

vendredi 16 octobre 2015

A mass of solar material gathered itself into a twisting mass, spun around for a bit, then rose up and broke apart over a 10-hour period on Oct. 13, 2015. Prominences are unstable clouds of gas tethered above the surface of the sun by magnetic forces.

Hefty Prominence Eruption Observed by SDO on October 13, 2015

The image and video were produced with a combination of two wavelengths of extreme ultraviolet light, 193 and 304 Angstroms. Though invisible to our eyes, these wavelengths are typically colorized in bronze and red, respectively. Much of the jittering and odd jumping motions above the surface were artifacts caused by brightening and contrast changes used to bring out the detail and structure of the prominence.

Image above: This image was taken by the Long Range Reconnaissance Imager (LORRI) on NASA's New Horizons spacecraft shortly before closest approach to Pluto on July 14, 2015; it resolves details as small as 270 yards (250 meters). The scene shown is about 130 miles (210 kilometers) across. The sun illuminates the scene from the left, and north is to the upper left. Image Credits: NASA/JHUAPL/SwRI.

It seems that the more we see of Pluto, the more fascinating it gets. With its prominent heart-shaped feature, icy mountains, and “snakeskin” terrain, Pluto has already surprised New Horizons scientists with the variety and complexity of its surface features.

Now this latest image, from the heart of Pluto’s heart feature, show the plains’ enigmatic cellular pattern (at left) as well as unusual clusters of small pits and troughs (from lower left to upper right).

Scientists believe that this area, informally known as Sputnik Planum, is composed of volatile ices such as solid nitrogen. They theorize that the pits and troughs – typically hundreds of meters across and tens of meters deep – are possibly formed by sublimation or evaporation of these ices. However, the reasons for the striking shapes and alignments of these features are a mystery. Adding to the intrigue is that even at this resolution, no impact craters are seen, testifying to the extreme geologic youth of Sputnik Planum.

“Pluto is weird, in a good way,” said Hal Weaver, New Horizons project scientist with Johns Hopkins Applied Physics Laboratory in Laurel, Maryland. “The pits, and the way they’re aligned, provide clues about the ice flow and the exchange of volatiles between the surface and atmosphere, and the science team is working hard to understand what physical processes are at play here.”

New Horizons Pluto flyby. Image Credits: NASA/JPL

New Horizons is part of NASA’s New Frontiers Program, managed by the agency’s Marshall Space Flight Center in Huntsville, Alabama. The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, designed, built, and operates the New Horizons spacecraft and manages the mission for NASA’s Science Mission Directorate. SwRI leads the science mission, payload operations, and encounter science planning.

At 23:49 MSK (21:49 GMT) space head part (upper stage and spacecraft)
cleanly separated from the third stage of the launch vehicle and entered
the calculated orbit.

Upper stage Breeze-M and TURKSAT-4B at the top

Further injection into the target orbit carried the upper stage Breeze-M. The total duration of excretion from the start of the launcher before separation of the spacecraft will be 9 hours and 13 minutes, separating the spacecraft Turksat-4B is scheduled for 8:53 MSK (6:53 GMT) on 17 October 2015.

Satellite Use:

TURKSAT-4B satellite

TURKSAT-4B is a commercial communication satellite built by Mitsubishi Electric. The satellite will provide telecommunication and direct TV broadcasting services over a wide geographic region between west of China and east of England spanning Turkey, as well as Europe, Central Asia, the Middle East and Africa. TURKSAT-4B will be positioned at 50 degrees east longitude and consists of multiple transponders with an expected on-orbit maneuver life of 30 years. TURKSAT-4B satellite will expand the space capacity of Turkey and provide enhanced performance to its coverage areas. The satellite will provide high flexibility of switchability and connectivity among different service areas to its customers.

This launch was the fifth since the beginning of 2015, the successful launch in to the space using a carrier rocket Proton-M. Previous launch rocket Proton-M took place on September 14 2015 with a Russian communications satellite Express-AM8.

ESA’s first technology-testing CubeSat, released last week from the International Space Station, is in good health and is set to start work on its six-month mission.

“This tiny satellite was developed in only a year and now we are very pleased with the rapid progress made during the first few days in orbit to check its readiness for its mission,” notes Roger Walker, overseeing ESA’s technology CubeSat effort.

CubeSats deployed

GomX-3 was designed and built for ESA by Denmark’s Gomspace company. Engineer David Gerhardt adds: “Following its release from the Station on 5 October, much of the satellite’s proving phase is complete, demonstrating that it is operational and in good health.

“We are now taking the first steps towards putting its technology payloads through their paces.”

Despite its small size of 10x10x30 cm, the nanosatellite precisely controls its orientation by spinning miniaturised ‘reaction wheels’ at varying speeds.

This precision is an important factor in the effectiveness of the mission’s technology-testing payloads.

One task will see GomX-3 pointing up towards to detect radio signals from telecom satellites in geostationary orbit to assess their overall transmission efficiency.

GomX-3 CubeSat

The processing software can be changed in flight, allowing the receiver to be reconfigured and used in extremely flexible ways, of wider interest for future ESA missions.

The CubeSat also carries a miniaturised version of a transmitter being flown on ESA’s Proba-V minisatellite for downloading data rapidly at X-band radio frequencies. Developed by the French Syrlinks company in cooperation with France’s CNES space agency, the antenna will aim at X-band ground stations in the CNES network.

Once the communications link has been tested over the coming months, the transmitter will be available to fly on future nanosatellites to boost their amount of downloaded data.

GomX-3 also sports a receiver to detect navigation signals from aircraft. The satellite points its distinctive helical antenna to Earth and has already picked up a tens of thousands of Automatic Dependent Surveillance – Broadcast, or ADS-B, signals from aircraft since the day after launch.

ESA’s 2013-launched Proba-V first confirmed the feasibility of ADS-B detection from orbit, opening up the prospect of a global aircraft monitoring system incorporating remote regions not covered by ground-based air traffic control.

GomX-3 being built

Gomspace’s GomX-1, launched in 2013 and still operational, showed ADS-B detection could also be performed from smaller satellites, like CubeSats. GomX-3’s receiver is an improved design.

“This is the first of many ESA nanosatellite missions,” concludes Roger. “Our aim is to test new technologies and techniques or fly promising payloads in a more rapid affordable way, with more CubeSat launches next year.”

jeudi 15 octobre 2015

Cassini spacecraft has begun returning its best-ever views of the northern extremes of Saturn's icy, ocean-bearing moon Enceladus. The spacecraft obtained the images during its Oct. 14 flyby, passing 1,142 miles (1,839 kilometers) above the moon's surface. Mission controllers say the spacecraft will continue transmitting images and other data from the encounter for the next several days.

Scientists expected the north polar region of Enceladus to be heavily cratered, based on low-resolution images from the Voyager mission, but the new high-resolution Cassini images show a landscape of stark contrasts. "The northern regions are crisscrossed by a spidery network of gossamer-thin cracks that slice through the craters," said Paul Helfenstein, a member of the Cassini imaging team at Cornell University, Ithaca, New York. "These thin cracks are ubiquitous on Enceladus, and now we see that they extend across the northern terrains as well."

Cassini's next encounter with Enceladus is planned for Oct. 28, when the spacecraft will come within 30 miles (49 kilometers) of the moon's south polar region. During the encounter, Cassini will make its deepest-ever dive through the moon's plume of icy spray, sampling the chemistry of the extraterrestrial ocean beneath the ice. Mission scientists are hopeful data from that flyby will provide evidence of how much hydrothermal activity is occurring in the moon's ocean, along with more detailed insights about the ocean's chemistry -- both of which relate to the potential habitability of Enceladus.

Cassini's final close Enceladus flyby will take place on Dec. 19, when the spacecraft will measure the amount of heat coming from the moon's interior. The flyby will be at an altitude of 3,106 miles (4,999 kilometers).

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA's Jet Propulsion Laboratory in Pasadena, California, manages the mission for the agency's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. The Cassini imaging operations center is based at the Space Science Institute in Boulder, Colorado.

From Pluto’s unusual heart-shaped region to its extended atmosphere and intriguing moons, New Horizons has revealed a degree of diversity and complexity in the Pluto system that few expected in the frigid outer reaches of the solar system.

Image above: This high-resolution image captured by NASA’s New Horizons spacecraft combines blue, red and infrared images taken by the Ralph/Multispectral Visual Imaging Camera (MVIC). The bright expanse is the western lobe of the “heart,” informally called Sputnik Planum, which has been found to be rich in nitrogen, carbon monoxide and methane ices. Image Credits: NASA/JHUAPL/SwRI.

The New Horizons team describes a wide range of findings about the Pluto system in its first science paper, released today. “The Pluto System: Initial Results from its Exploration by New Horizons,” led by mission Principal Investigator Alan Stern, appears as the cover story in the Oct. 16 issue of Science, just three months after NASA’s historic first exploration of the Pluto system in July.

“The New Horizons mission completes our initial reconnaissance of the solar system, giving humanity our first look at this fascinating world and its system of moons,” said Jim Green, director of planetary science at NASA Headquarters in Washington. “New Horizons is not only writing the textbook on the Pluto system, it’s serving to inspire current and future generations to keep exploring—to keep searching for what’s beyond the next hill.”

NASA’s New Horizons spacecraft reached a distance of 7,750 miles (12,500 kilometers) from Pluto’s surface during its July 14 closest approach, gathering so much data it will take almost another year to return to Earth. The data returned so far show a surprisingly wide variety of landforms and terrain ages on Pluto, as well as variations in color, composition and albedo (surface reflectivity). Team members also discovered evidence for a water-ice rich crust, multiple haze layers above the surface in Pluto’s atmosphere, and that Pluto is somewhat larger and a bit more ice rich than expected.

“The Pluto system surprised us in many ways, most notably teaching us that small planets can remain active billions of years after their formation,” said Stern, with the Southwest Research Institute (SwRI) in Boulder, Colorado. “We were also taught important lessons by the degree of geological complexity that both Pluto and its large moon Charon display.”

Some of the processes on Pluto appear to have occurred geologically recently, including those that involve the water-ice rich bedrock as well as the more volatile, and presumably more mobile, ices of the western lobe of Pluto’s “heart.” The diverse geology and apparent recent activity raise fundamental questions about how small planetary bodies remain active many billions of years after formation. The research suggests that other large worlds in the Kuiper belt -- such as Eris, Makemake, and Haumea -- could also have similarly complex histories that rival those of terrestrial planets such as Mars and Earth.

The New Horizons team notes that Triton, likely a former Kuiper Belt planet captured by Neptune, was considered the best analog for Pluto prior to the July 14 flyby. The team now believes that the geologies of Triton and Pluto are more different than similar, but will know more as additional data are returned.

New Horizons is part of NASA’s New Frontiers Program, managed by the agency’s Marshall Space Flight Center in Huntsville, Alabama. The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, designed, built, and operates the New Horizons spacecraft and manages the mission for NASA’s Science Mission Directorate. SwRI leads the science mission, payload operations, and encounter science planning.

The sea ice cover of the Southern Ocean reached its yearly maximum extent on Oct. 6. At 7.27 million square miles (18.83 million square kilometers), the new maximum extent falls roughly in the middle of the record of Antarctic maximum extents compiled during the 37 years of satellite measurements – this year’s maximum extent is both the 22nd lowest and the 16th highest. More remarkably, this year’s maximum is quite a bit smaller than the previous three years, which correspond to the three highest maximum extents in the satellite era, and is also the lowest since 2008.

2015 Antarctic Maximum Sea Ice Extent Breaks Streak of Record Highs

Video above: Antarctic sea ice likely reached its annual maximum extent on Oct. 6, barring a late season surge. This video shows the evolution of the sea ice cover of the Southern Ocean from its minimum yearly extent to its peak extent. Video Credits: NASA's Goddard Space Flight Center.

The growth of Antarctic sea ice was erratic this year: sea ice was at much higher than normal levels throughout much of the first half of 2015 until, in mid-July, it flattened out and even went below normal levels in mid-August. The sea ice cover recovered partially in September, but still this year’s maximum extent is 513,00 square miles (1.33 million square kilometers) below the record maximum extent, which was set in 2014. Scientists believe this year’s strong El Niño event, a natural phenomenon that warms the surface waters of the eastern equatorial Pacific Ocean, had an impact on the behavior of the sea ice cover around Antarctica. El Niño causes higher sea level pressure, warmer air temperature and warmer sea surface temperature in the Amundsen, Bellingshausen and Weddell seas in west Antarctica that affect the sea ice distribution.

Antarctic sea ice max 2015. Image Credit: Goddard Space Flight Center

“After three record high extent years, this year marks a return toward normalcy for Antarctic sea ice,” said Walt Meier, a sea ice scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “There may be more high years in the future because of the large year-to-year variation in Antarctic extent, but such extremes are not near as substantial as in the Arctic, where the declining trend towards a new normal is continuing.”

This year’s maximum extent occurred fairly late: the mean date of the Antarctic maximum is Sept. 23 for 1981-2010.

Catastrophic flooding triggered by ice melting from the heat of volcanic activity is thought to be responsible for the chaotic scenery depicted in this region of the Mangala Valles channel network.

The images were taken by the high-resolution stereo camera on ESA’s Mars Express on 12 July just to the south of the mouth of Minio Vallis. The region is part of the Mangala Valles outflow channel system, and is situated in the southwestern portion of the Tharsis bulge, home to several volcanoes, including the Solar System’s largest: Olympus Mons.

Mangala Valles in context

The region’s proximity to these volcanic giants likely played an important role in creating the channels seen in these images, which were carved by large volumes of flowing water.

The source of the water is believed to be related to the formation of the Mangala Fossae, an east–west fault system spanning several hundreds of kilometres to the south of the region seen here.

There, hot, molten rock could have reached the surface in an episode of increased volcanic activity during the formation of the Tharsis bulge.

Perspective view of eroded crater in Mangala Valles

This activity may have triggered the melting of subsurface ice, and consequently the formation of the water-carved channels.

Several basins and impact craters were also filled with water, with overflows flushing through multiple spillways and towards Amazonis Planitia, the lowlands to the north. For example, a channel drains into the 28 km-wide impact crater in the upper right of the main image, breaching its crater wall.

3D view of eroded crater in Mangala Valles

The crater in the centre of the image has a somewhat different appearance: it was filled with water and sediments and later eroded back again. ‘Chaotic terrain’ formed around it, characterised by isolated blocks of surface material that have been chaotically arranged during the release of subsurface water and subsequent surface collapse.

Another example of an infilled and eroded crater lies to the southeast (bottom left in the main image) of this crater.

The chaotic terrain suggests this region may also have had subsurface ice, which experienced multiple episodes of melting and flooding.

Mangala Valles topography

A deep channel carves through the landscape along the bottom edge of the image, its inner walls displaying layers, terraces and streamlined islands eroded by the outflowing water.

Mangala Valles is estimated to have been created during the Hesperian epoch about 3.5 billion years ago, with episodes of both volcanic and flooding activity likely continuing into the Amazonian age, perhaps as recently as a few hundred million years ago.

mercredi 14 octobre 2015

The term “space fog” refers not to water droplets blocking the view in space – there’s no water out there – but rather a phenomenon affecting the mental abilities of astronauts. Those who have spent time aboard the International Space Station coined the term to describe the difficulty concentrating and mental fatigue they sometimes experience.

Astronauts need to maintain a high level of mental performance, so scientists need a tool to objectively measure how spaceflight changes that performance – the density of the fog, if you will. An investigation called Cognition is evaluating the in-flight use of one such tool, a comprehensive battery of computerized tests.

The battery includes 10 different cognitive tests and lasts about 20 minutes. Crew members will complete the battery 11 times during six months aboard the station. The tests cover a wider range of mental or cognitive functions than can be currently assessed in space and provide immediate, real-time feedback on performance.

Designing the series of tests took about four years, said principal investigator Mathias Basner, an associate professor at the University of Pennsylvania Perelman School of Medicine who holds an M.D. and Ph.D. in research. The tests couldn’t be too easy, which might bore astronauts, or too hard, which might cause frustration. The entire battery couldn’t take too long, either, as time is very valuable in space.

In addition, the tests need to evaluate a variety of brain functions in order to create a clear picture of astronaut health and performance capability. The battery covers cognitive abilities such as working memory, stability of attention, and sensory motor speed; emotional recognition, such as whether a subject can “read” a fellow astronauts’ face; a subject’s willingness to take the appropriate amount of risk in decision-making; and spatial orientation, a critical ability in microgravity.

The problem of space fog is hardly surprising. In space, astronauts deal with disruption of sleep and daily rhythms, heavy mental and physical workloads, and environmental stressors such as microgravity, high levels of carbon dioxide, and radiation. There are also psychological issues related to isolation and confinement.

Image above: As part of his Year in Space, NASA astronaut Scott Kelly regularly takes a test battery for the Cognition investigation on the International Space Station. Image Credit: NASA.

“We have done other work on understanding what kind of things impair cognitive ability,” said co-investigator David F. Dinges, a professor in the University of Pennsylvania Department of Psychiatr, who holds a Ph.D. in physiological psychology. “We know that sufficient length and quality of sleep is paramount for performing at high levels, yet astronauts on the station often get six or fewer hours of sleep every 24 hours. That is comparable to chronic sleep deprivation, which we know causes impairment.”

Scientists do not yet know the exact role of fatigue in causing space fog, or that of other physical effects of spaceflight such as changes in vision, higher pressure in the brain, or medications used to manage sleep and fatigue. For the most part, all they have are subjective reports of problems from the astronauts themselves.

“There can be a huge disconnect between subjective and objective assessment, especially during sleep deprivation,” Basner said. “You just get used to feeling tired and think that is normal, and then you may overestimate your performance capability.”

As highly-trained, highly-effective individuals, astronauts also may be able to better compensate, at least temporarily. Data from the test battery provide an objective, rather than subjective, measure of an astronaut’s level of impairment and the role various stressors play.

Image above: Screenshots of 10 of the tests used to measure cognitive function in space. Image Credit: University of Pennsylvania.

Researchers also have been giving the tests on the ground to astronauts, astronaut candidates, and subjects from mission control. The data from these tests show how a similar population performs in normal gravity, which then can be compared to data from space.

The test battery could be useful in a variety of situations on Earth.

“This is designed for high-performing individuals, not necessarily for a standard population,” said Basner. “But it could be administered to medical doctors, who have problems with fatigue, or to pilots, for example. We’ve implemented it with scientists in Antarctica, an environment with some of the same challenges as space.”

The level of difficulty of the tests could be adjusted for other uses as well, such as assessing whether mental changes represent normal aging or signs of dementia.

By enabling more effective measurement of the performance of crew members in space or populations on the ground, the test battery should help clear up the fog.

The dark area across the top of the sun in this image is a coronal hole, a region on the sun where the magnetic field is open to interplanetary space, sending coronal material speeding out in what is called a high-speed solar wind stream. The high-speed solar wind originating from this coronal hole, imaged here on Oct. 10, 2015, by NASA's Solar Dynamics Observatory, created a geomagnetic storm near Earth that resulted in several nights of auroras. This image was taken in wavelengths of 193 Angstroms, which is invisible to our eyes and is typically colorized in bronze.

Dark smudges almost block out a rich star field in this new image captured by the Wide Field Imager camera, installed on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. The inky areas are small parts of a huge dark nebula known as the Coalsack, one of the most prominent objects of its kind visible to the unaided eye. Millions of years from now, chunks of the Coalsack will ignite, rather like its fossil fuel namesake, with the glow of many young stars.

The Coalsack Nebula in the constellation of Crux

The Coalsack Nebula is located about 600 light-years away in the constellation of Crux (The Southern Cross). This huge, dusky object forms a conspicuous silhouette against the bright, starry band of the Milky Way and for this reason the nebula has been known to people in the southern hemisphere for as long as our species has existed.

Wide-field view of part of the Coalsack Nebula

The Spanish explorer Vicente Yáñez Pinzón first reported the existence of the Coalsack Nebula to Europe in 1499. The Coalsack later garnered the nickname of the Black Magellanic Cloud, a play on its dark appearance compared to the bright glow of the two Magellanic Clouds, which are in fact satellite galaxies of the Milky Way. These two bright galaxies are clearly visible in the southern sky and came to the attention of Europeans during Ferdinand Magellan’s explorations in the 16th century. However, the Coalsack is not a galaxy. Like other dark nebulae, it is actually an interstellar cloud of dust so thick that it prevents most of the background starlight from reaching observers.

Zooming in on the dark and dusty Coalsack Nebula

A significant number of the dust particles in dark nebulae have coats of frozen water, nitrogen, carbon monoxide and other simple organic molecules. The resulting grains largely prevent visible light from passing through the cosmic cloud. To get a sense of how truly dark the Coalsack is, back in 1970, the Finnish astronomer Kalevi Mattila published a study estimating that the Coalsack has only about 10 percent of the brightness of the encompassing Milky Way. A little bit of background starlight, however, still manages to get through the Coalsack, as is evident in the new ESO image and in other observations made by modern telescopes.

A close look at part of the Coalsack Nebula

The little light that does make it through the nebula does not come out the other side unchanged. The light we see in this image looks redder than it ordinarily would. This is because the dust in dark nebulae absorbs and scatters blue light from stars more than red light, tinting the stars several shades more crimson than they would otherwise be.

Millions of years in the future the Coalsack’s dark days will come to an end. Thick interstellar clouds like the Coalsack contain lots of dust and gas — the fuel for new stars. As the stray material in the Coalsack coalesces under the mutual attraction of gravity, stars will eventually light up, and the coal “nuggets” in the Coalsack will "combust", almost as if touched by a flame.

More information:

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Imagine beaming a light across millions of kilometres of empty space, all the way back to Earth. ESA’s proposed Asteroid Impact Mission is intended to do just that: demonstrate laser communications across an unprecedented void.

Laser communication with Earth

The Asteroid Impact Mission, or AIM, undergoing detailed design ahead of a final go/no-go decision by ESA’s Ministerial Council in December 2016, is a deep-space technology-demonstration mission that would also be humanity’s first probe to a double asteroid.

Among its innovative technologies, laser communications would return results to scientists several times faster than standard radio signals.

“Optical communications in general is not yet a well-established technology for space and ESA’s European Data Relay System (EDRS) will be the first commercial application,” explains ESA optics engineer Zoran Sodnik.

ESA’s laser station

“In principle it works something like Morse code, with encoded rapid flashes on and off. ERDS with satellites in high orbits will use laser links to return environmental data from Europe’s low-orbiting Sentinel satellites on a realtime basis, a technique previously demonstrated using ESA’s Alphasat and Artemis telecom missions.

“But AIM will need to operate much further: we are benchmarking a maximum span of 75 million kilometres, or half the distance between Earth and the Sun. That might sound like a lot, but operating around Mars one day will involve much further distances still.”

Transmitter telescope

A laser beam shone back from AIM’s 13.5 cm-diameter laser telescope at such a distance would have a ground footprint of about 1100 km – further than from London to Berlin. Also a lot but the equivalent radio beam radiating out across space would end up wider than our whole planet.

“The much higher frequency of laser light is what gives us higher directivity and as a result increased bandwidth,” adds ESA laser engineer Clemens Heese.

“At the same time, many photons will get lost on the way, so we need to use sophisticated photon counting methods to detect the signal reliably using our receiver telescope of around 1 m diameter.

AIM laser

“While radio communications is a very mature technology and close to optimum efficiency, there’s still lots of room for development with optical communications. So this is the way we need to go to really boost the quantity and speed of data we can deliver to scientists.”

To meet the challenge, ESA’s AIM team this month issued technology pre-development contracts to industry to tackle key issues including telescope design, detector electronics and coarse and fine-pointing systems. To give an idea of the kind of pointing required, AIM will need to align with the signal from Earth to within the diameter of planet Mars seen in our terrestrial sky.

Laser for altimetry

“At 39.3 kg, AIM’s laser system will be one of the single largest payload items,” explains Andres Galvez, heading ESA’s General Studies Programme.

“We intend to gain maximum utility from it, by also using it for scientific purposes: the laser can also serve as an altimeter to chart the asteroid.”

Earth defense test

The system design is led by RUAG Space in Switzerland, building on its existing family of Optel laser communication terminals, the latest of which is tailored for direct-to-Earth downlinks from minisatellites.

NASA's Cassini spacecraft will wrap up its time in the region of Saturn's large, icy moons with a series of three close encounters with Enceladus starting Wednesday, Oct. 14. Images are expected to begin arriving one to two days after the flyby, which will provide the first opportunity for a close-up look at the north polar region of Enceladus.

Wednesday’s flyby is considered a moderately close approach for Cassini, which will pass at an altitude of 1,142 miles (1,839 kilometers) above the moon's surface. Closest approach to Enceladus will occur at 6:41 a.m. EDT (3:41 a.m. PDT). The spacecraft’s final two approaches will take place in late October and mid-December.

During Cassini’s early-mission encounters with the moon, the northern terrain of Enceladus was masked by wintry darkness. Now that the summer sun is shining on the high northern latitudes, scientists will be looking for signs of ancient geological activity similar to the geyser-spouting, tiger-stripe fractures in the moon's south polar region. Features observed during the flyby could help them understand whether the north also was geologically active at some time in the past.

Image above: Earlier in Cassini's mission at Saturn, northern terrains on the ocean-bearing icy moon Enceladus were in the shadow of winter. Image Credits: NASA/JPL-Caltech.

"We've been following a trail of clues on Enceladus for 10 years now," said Bonnie Buratti, a Cassini science team member and icy moons expert at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. "The amount of activity on and beneath this moon's surface has been a huge surprise to us. We're still trying to figure out what its history has been, and how it came to be this way."

Since Cassini's 2005 discovery of continually-erupting fountains of icy material on Enceladus, the Saturn moon has become one of the most promising places in the solar system to search for present-day habitable environments. Mission scientists announced evidence in March that hydrothermal activity may be occurring on the seafloor of the moon's underground ocean. In September they broke news that its ocean -- previously thought to be only a regional sea -- was, in fact, global.

"The global nature of Enceladus' ocean and the inference that hydrothermal systems might exist at the ocean's base strengthen the case that this small moon of Saturn may have environments similar to those at the bottom of our own ocean," said Jonathan Lunine, an interdisciplinary scientist on the Cassini mission at Cornell University in Ithaca, New York. "It is therefore very tempting to imagine that life could exist in such a habitable realm, a billion miles from our home."

The Oct. 14 encounter will serve as a prelude to the main event, a flyby of Enceladus on Wednesday, Oct. 28, during which Cassini will come dizzyingly close to the icy moon, passing a mere 30 miles (49 kilometers) above the moon's south polar region. During this encounter, Cassini will make its deepest-ever dive through the moon's plume of icy spray, collecting images and valuable data about what's going on beneath the frozen surface. Cassini scientists are hopeful data from that flyby will provide evidence of how much hydrothermal activity is occurring in the moon's ocean, and how the amount of activity impacts the habitability of Enceladus’ ocean.

Cassini's final close flyby on Dec. 19 will examine how much heat is coming from the moon's interior from an altitude of 3,106 miles (4,999 kilometers).

An online toolkit for all three final Enceladus flybys is available at:

Cassini arrived at Saturn in 2004 and still has about two years left on its mission. Beginning in November, mission controllers will begin to slowly raise Cassini's orbit out of the space around the Saturn’s equator, where flybys of the large moons are more common. Coming up are a number of closest-ever brushes with the small moons that huddle near the planet's rings.

"We'll continue observing Enceladus and its remarkable activity for the remainder of our precious time at Saturn," said Linda Spilker, Cassini project scientist at JPL. "But these three encounters will be our last chance to see this fascinating world up close for many years to come."

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. JPL manages the mission for NASA's Science Mission Directorate in Washington.